DATAJDBC-318 - Add support for Query Derivation

[mp911de]

We now support query derivation for repository query methods. Query methods support a wide range of keywords including support for embedded entities. Query derivation is limited to properties that can be used in a WHERE clause without involving joins.

interface PersonRepository extends PagingAndSortingRepository<Person, String> {

  List<Person> findByFirstname(String firstname);                                   

  List<Person> findByFirstnameOrderByLastname(String firstname, Pageable pageable); 

  Person findByFirstnameAndLastname(String firstname, String lastname);             

  Person findFirstByLastname(String lastname);
	
  Person findByAddress(Address address);
	
  Person findByAddressStreet(String street);
}

class Person {

  @Id String id;
  String firstname, lastname;
	@Embedded.Nullable Address address;	
}

class Address {
  String city, street;
}

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Related ticket: DATAJDBC-318.

[schauder]

One major complaint:

The select generation doesn't work properly for Entities that have 1:1 and 1:M relationships.

Iseeker pointed this out in a comment on the issue all ready https://jira.spring.io/browse/DATAJDBC-318?focusedCommentId=188768&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-188768

208cee4 adds two quick tests to demonstrate the problem.

The underlying problem is: We really shouldn't have two places where the base select gets constructed.
It is rather complex and will change in the future when we want to support more efficient ways of querying.

[schauder]

Just using SELECT * doesn't work if there are 1:1 references in the aggregate, because these require a join and special aliases in order to avoid name clashes.

[schauder]

Merged to master.